1. Field of the Invention
The invention relates to a nonvolatile semiconductor memory device and a method for manufacturing the same including a plurality of isolation dielectric films and a plurality of electrode films alternately stacked on a substrate.
2. Background Art
Flash memory conventionally is constructed by two-dimensionally integrating elements on a surface of a silicon substrate. In such flash memory, the dimensions of each element must be reduced for downscaling to increase the memory capacity. However, such downscaling in recent years has become difficult in regard to both cost and technology.
To solve such problems, a collectively-patterned three-dimensional stacked memory has been proposed (for example, refer to JP-A 2007-266143 (Kokai)). In such technology, a stacked body is formed on a silicon substrate by alternately stacking an electrode film and an isolation dielectric film, and then forming through-holes in the stacked body by collective patterning. A charge storage layer is formed on a side face of each through-hole, and silicon is filled into an interior of the through-hole to form a silicon pillar. A cell transistor is thereby formed at an intersection between each electrode film and each silicon pillar. In such a collectively-patterned three-dimensional stacked memory, a charge can be removed from and put into the charge storage layer from the silicon pillar to record information in the cell transistor by controlling an electrical potential of each electrode film and each silicon pillar. According to such technology, the cell transistors can be three-dimensionally integrated, and the memory capacity can be increased. Moreover, the three-dimensional stacked memory can be formed by collectively patterning the stacked body. Therefore, the number of lithography processes does not increase, and the cost can be prevented from increasing even in the case where the number of stacks increases.
However, it is unfortunately difficult to provide both sufficient ON/OFF characteristics of the cell transistor and endurance to stress during writing/erasing in such a collectively-patterned three-dimensional stacked memory.